Level Meter - RME Audio Fireface 400 User Manual

30.14 Level Meter

The Fireface 400 calculates all the display values Peak, Over and RMS in hardware, in order to
be capable of using them independent of the software in use, and to significantly reduce the
CPU load.
Tip: This feature, the Hardware Level Meter, is used by DIGICheck (see chapter 16 / 23) to
display Peak/RMS level meters of all channels, nearly without any CPU load.
The level meters integrated in TotalMix - considering their size - cannot be compared with
DIGICheck. Nevertheless they already include many useful functions.
Peak and RMS is displayed for every channel. 'Level Meter Setup' (menu Options or F2) and
direct keyboard hotkeys offer various options:
•
Display range 40 or 60 dB (hotkey 4 or 6)
•
Release time of the Peak display (Fast/Medium/Slow)
•
Numerical display selectable either Peak or RMS (Hotkey E or R)
•
Number of consecutive samples for Overload display (1 to 15)
•
RMS display absolute or relative to 0 dBFS (Hotkey 3 or 0)
The latter is a point often overlooked, but none-
theless important. A RMS measurement shows
3 dB less for sine signals. While this is mathe-
matically correct, it is not very reasonable for a
level meter. Therefore the RMS readout is
usually corrected by 3 dB, so that a full scale
sine signal shows 0 dBFS on both Peak and
RMS meters. This setting also yields directly
readable signal-to-noise values. Otherwise the
value shown with noise is 3 dB better than it
actually is (because the reference is not 0 dB,
but -3 dB).
The value displayed in the text field is inde-
pendent of the setting 40/60 dB, it represents
the full 24 bit range of the RMS measurement.
An example: An RME ADI-8 QS connected to
the Fireface's ADAT port will yield a display of
around -114 dBFS on all eight channel's input
level meters.
This level display of TotalMix also provides means for a constant monitoring of the signal qual-
ity. Thus it can be a valuable tool for sound optimization and error removal in the studio.
Measuring SNR (Signal to Noise) is best done with RME's free software DIGICheck. The
function Bit Statistic includes three different RMS meters for exactly this purpose (RMS un-
weighted, A-weighted and DC).
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User's Guide Fireface 400 © RME